Kendo UI dropdownlist 后台绑定默认值

                               <div style="display:block;float:left;width:100%;min-width:175px;height:80%;margin-top:7px">
                                    <input id="Exp_Position" inputRequired="required" onblur="inputRequiredChange(this)"
                                           data-role="dropdownlist"
                                           data-text-field="Exp_PositionName"
                                           data-value-field="Exp_PositionID"
                                           data-filter="contains"
                                           data-bind="value:expenseApply.Exp_PositionID, source:PositionResource,events:{change:PositionChange}">
                                    <span class='k-widget k-tooltip k-tooltip-validation field-validation-error k-required' style="display:none;position: absolute;top: 90%;left: 0;">职务不能为空</span>
                                </div>

 //职务数据源
        PositionResource: new kendo.data.DataSource({
            transport: {
                read: {
                    url: "/BaseData/PositionList"
                }
            },
            schema: {
                model: {
                    id: "Exp_PositionID"
                }
            },
            requestEnd: function (res) {
                if (res && res.response && res.response.length > 0) {
                    var defaultPosition = _.find(res.response, function (t) {
                        return t.IsDefault;
                    });
                    console.log(expenseApplyCreateViewModel.expenseApply);
                    if (defaultPosition) {
                        expenseApplyCreateViewModel.expenseApply.set("Exp_PositionID", defaultPosition.Exp_PositionID);
                        expenseApplyCreateViewModel.expenseApply.set("Exp_PositionName", defaultPosition.Exp_PositionName);
                    }
                }
            }
        }),

/// <summary>
        /// 职务数据源
        /// </summary>
        /// <returns></returns>
        [Data]
        public ActionResult PositionList()
        {
            ExpInnerOrderService proc = new ExpInnerOrderService();
            List<CndModel> pars = new List<CndModel>();
            //pars.Add(new CndModel("(USER_CODE  = '" + UserContext.UserID + "')"));
            var result = proc.GetExpOraclePositionList( pars, "order by JOB_CID ");

            if (!result.IsNullOrCountZero())
            {
               var defaultPosition= result.FirstOrDefault();
                defaultPosition.IsDefault = true;
            }

            result.SetRowindx();
            return Json(result, JsonRequestBehavior.AllowGet);
        }